Adjustable ferroresonant transformer

ABSTRACT

A ferroresonant transformer having a mechanical adjustment in the limiting cross section of the core linking the secondary windings provided by a movable rectilinear segment in the leg on which the secondary is wound, with the longitudinal axes of movement of the segment being canted with respect to the axes of the leg so as to constitute an offset portion of the leg presenting a decreasing limiting cross section as the segment is withdrawn along its axis.

United States Patent Hoffman, Jr.

[451 Mar. 14,1972

[54] ADJUSTABLE FERRORESONANT TRANSFORMER [72] Inventor: Harry S. Hoffman, Jr., Saugerties, N.Y.

[73] Assignee: International Business Machines Corporation, Armonk, N.Y.

[22] Filed: July30, 1970 21 App1.No.: 59,406

[52] U.S.Cl. ..336/l32,33 6/l33 [51] lnt.Cl. ..ll01f2l/06 [58] FieldofSearch ..336/l30,132,133,134

[56] References Cited UNITED STATES PATENTS 2,248,070 7/1941 Fanger ..336/133 2,567,617 9/1951 Pedersen.... .....336/133 3,254,318 5/1966 Steinert ..336/133 5 2,869,087 1/1959 Sontheimer ..336/133X 3,127,580 3/1964 Owen ..336/133 FOREIGN PATENTS OR APPLICATIONS 762,685 1/1934 France .Q ..336/133 742,905 12/ 1 943 Germany ..336/134 846,133 8/1952 Germany ..336/134 Primary Examiner-Thomas J. Kozma Attorney-Hanifin and Jancin and Frederick D. Poag [57] ABSTRACT 12 Claims, 3 Drawing Figures PAIENTEUMAR 141912 FIG.3

E OUT mow cRoss sscnou m we H 100 USEFUL OPERATING RANGE ATTORNEY ADJUSTABLE FERRORESONANT TRANSFORMER CROSS-REFERENCE TO RELATED APPLICATION U.S. Pat. application Ser. No. 59,405, filed on the same day as this application and assigned to the same assignee, is a related application.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to voltage regulating transformers and more particularly to adjustable output ferroresonant voltage regulating transformers wherein the output voltage is alterable by a change in the saturating flux level in the-magnetic path linking the output windings.

2. Description of the Prior Art Ferroresonant regulating transformers of the type disclosed, for example, in U.S. Pat. No. 2,143,745, issued Jan. I0, 1939,

to Joseph G. Sola and entitled Constant Potential Transformer depend for their regulated output on a constant flux level in the magnetic core path linking the output winding. This constant flux level is achieved by applying a limited primary MMF to the secondary core path while maintaining that core segment at saturation whereby the flux therein is substantially constant. Usually, this saturation is achieved by operation of a resonant circuit comprising a portion of the secondary winding in a tank circuit with a capacitor, and the limitation of primary MMF applied to the secondary core path is provided by shunting excess primary flux across a small airgap once secondary saturation has been achieved.

In a transformer of this kind, adjustment of the output is difficult to achieve since the magnetic path constitutes a fixed structure, the transformer is by its very nature insensitive to changes in the primary winding circuit, andthe operation of the secondary circuit is dominated by the fixed saturation flux of the secondary structure.

US. Pat. No. 3,148,326 issued Sept. 8, 1964, to O. M. Baycura et al., and entitled Ferroresonant Transformer with Saturating Control Winding addressed this problem by providing auxiliary windings for introducing a control flux and varying the effective cross section of a core section in the transformer to control the output voltage thereof.

SUMMARY OF THE INVENTION The present invention provides an infinitely variable gradation of output voltage in a ferroresonant regulating transfonner by provision of a movable segment in the core structure of the magnetic path linking the secondary windings. Adjustment of the position of the segment alters the limiting cross section of that flux path whereby saturation is achieved with a variable total flux. This movable segment is preferably straight sided with respect to its direction of movement so as to be operable in a simple sliding manner with respect to the cooperating parts of the stationary core structure. In a preferred embodiment the core structure is three legged, with the secondary core leg at its center, and the movable segment operates along an axis which is canted with respect to the centerline of that center leg in such fashion that the limiting cross section occurs within the secondary winding for minimization of leakage flux.

Accordingly, a principal object of the present invention is to provide an improved adjustable ferroresonant regulating transformer.

Another object of the invention is to provide an improved transformer as aforesaid wherein the adjustment is by simple mechanical means in the core structure.

Still another object of the invention is to provide a mechanical adjustment in a ferroresonant voltage regulating transformer as aforesaid which provides a limiting cross section in the magnetic core along a significant length within the secondary coil structure whereby leakage flux is minimized and accurate regulation enhanced.

Other objects of the invention will be apparent from the detailed description set forth hereinbelow and from the drawmg.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is a schematic diagram of a ferroresonant transformer embodying a preferred form of the invention.

DETAILED DESCRIPTION In FIG. 1 of the drawing, the illustrated ferroresonant transformer comprises a magnetic core generally designated 10,

having outer leg portions 10A and 10B and a center leg portion 10C joined by top and bottom end portions 12, 14. A primary winding 16 is positioned on primary portion 18 of center leg 10C and a secondary winding assembly 20 embraces secondary portion 22 of center leg 10C. Intermediate the primary and secondary portions 18, 22, center leg 10C is formed with laterally extending shunt portions 24, 26 adapted and arranged to form bypass magnetic paths including air gap 28,

l 30 for shunting flux between 10C and 10A, 10B. Gaps 28 and 30 are air gaps in the magnetic sense and may be filled with fiber or other materials to yield mechanical rigidity to the structure.

FIG. 2 is a circuit diagram corresponding to the transformer of FIG. 1, with primed numerals of FIG. 1 applied to the analogous symbols in FIG. 2. .For simplicity, the outer portions 10A, 10B, 12 and l4of the magnetic core structure of FIG. 1 are omitted in FIG. 2, it being understood that the symbolic showing indicates complete magnetic paths including the primary leg 18, the secondary leg 22, and shunt legs 24 and 26. The winding connections shown are typical for a ferroresonant voltage regulating transformer, the input terminals 32, 34 being connected to energize primary winding 16', and output terminals 36, 38 being connected to be energized by a portion 40 of the secondary winding 20'. In order to provide saturation of secondary magnetic core portion 22', a tank circuit is provided which, in the illustrated embodiment, comprises the entire secondary winding 20, across which is connected an external capacitor 42 to provide a resonant current in 40 in accordance with the general principles of operation of the aforementioned U.S. Pat. No. 2,143,745. It will be understood that the secondary winding could be more complex with various taps for different voltage outputs, and that the output 36, 38 could be taken across all of secondary winding 20 or across an auto transformer extension of the same, or across an independent heavier gauge secondary winding as may be convenient. Moreover, in some cases all or part of the capacitor effect can be provided by distributed capacity in the structure of secondary winding 20. These variations are given for example only and form no part, per se, of the present invention.

As aforesaid, the regulated output at terminals 36, depends in large part on the saturating level of flux through secondary core portions 22. In accordance with the present invention, means are provided to vary the limiting cross section of the core path linking secondary winding 20. In accordance with the illustrated preferred embodiment of the invention, this adjustable limiting section is provided in core portion 22 within winding 20 and is indicated by the arrow 44' in FIG. 2.

Returning to FIG. 1, this adjustment is provided by a slide member 44 which is adjustable between positions shown in full and phantom line to reduce the limiting cross section of the secondary portion 22 of center leg 10C from the full width value indicated at 50 to a reduced value shown at 52 as slide 44 is withdrawn from the core structure. Means such as an aperture 54 are provided by which slide 44 can be grasped to part bounded by sides 60, 62 which are transported along axis of movement 64 to assume positions shown by phantom lead lines 66, 68 as the limiting cross section is adjusted from that shown at 50 to that shown at 52.

The outer sides of the slide 44 are rectilinear and parallel to the axis of movement 64 so as to conform to rectilinear sides 80, 82 of the slot or aperture in core structure in which slide 44' moves. Accordingly, as long as the slide 44 is in engagement in slot 80, 82, communication is established through slide 44 from center leg 22 to the outer portions of top end 12 of the core structure. Preferably, the width of top end 12 is such that side 82 of the slot therein overlaps the abutting side of slide 44 to provide a flux path cross-sectional area at 84 which is always more than half the cross-sectional area at 52 for the same adjustment of slide 44. Accordingly, with limiting saturation occurring at 52, theflux in center leg 22 will divide approximately evenly between side legs 10A and 108 for efficient transformer operation.

Within these design considerations, the width of the upper portion of slide 44 is somewhat a matter of choice. Accordingly, in the illustrated embodiment the upper portion of slide 44 is widened beyond the width of the critical part 60, 62 to provide ample magnetic material surroun;ing aperture 54 so that the latter does not interfere with the magnetic flux paths approaching center leg portion 22 from the sides of top end portion 12.

The transformer structure illustrated in FIG. 1 can be manufactured conveniently by utilizing a stack of generally U- shaped lamina forming the side leg 10A and 10B and the bottom and portion 14, with the top portions of the U-shape being formed with parts bounding the slide slot edges 80, 82. Thus, the upper end of leg portion 10A fonns a part 86 of end portion 12 and continues through a neck area 88 to form a portion 90 of center leg 10C. The remainder of center leg 10C is formed by the part of slide 44 bounded by edges 60, 62 and by the center portion of a T-shaped stack of lamina, the stem of which forms the primary portion 18 of 10C and the lateral extensions of which form the shunt legs 24, 26. This arrangement provides for ease of assembly; the T-shaped portion forming 18, 24, 26 bearing primary winding 16 can be inserted into the window of the core after the secondary winding structure 20 has been inserted into that portion of the window and. then moved into the position shown embracing the secondary portion 22 of the core structure.

As illustrated in FIG. 3, a ferroresonant voltage regulating transformer of the illustrated kind provides an output voltage which rises slowly from zero as illustrated at 100 as the input voltage rises. When'the LC tank (20', 42 in FIG. 2) breaks into oscillation and the secondary core structure becomes saturated at its limiting cross section, the output voltage rises abruptly as seen at 102 and the transformer enters a useful operating range 104 wherein further increases in input voltage applied at terminals 32, 34 yield only small increases in the output voltage at terminals 36, 38. When slide 44 is adjusted to its position all the way into slot 80, 82 so that the limiting cross section of the secondary is as seen at 50, FIG. 1, the output at terminals 36, 38 is in accordance with the maximum output line 106 in FIG. 3. When the slide is withdrawn to the point of minimum operating position so that the limiting cross section is as indicated at 52 in FIG. 1, then the output voltage operating curve is as seen at 108 in FIG. 3. An intermediate setting would yield an output as seen at 110, and so on. Accordingly, the output of the transformer can be adjusted in infinite gradations and locked into any position of adjustment by means 56, 58in H6. 1. While a threaded bolt clamp 110, 112 is shown, of course any suitable means including a tight fit of the parts could be utilized to maintain the slide 44 in adjusted position.

Thus, while only one embodiment of the present invention has been illustrated in detail it will be understood that the invention may take other forms within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a ferroresonant transformer, a magnetic core structure comprising primary flux means and secondary flux means,

primary winding means linking said primary flux means and secondary winding means including resonating winding means linking said secondary flux means,

the improvement comprising mechanical adjustment means operable upon said magnetic core structure in said secondary flux means to vary substantially and continuously the limiting cross section of magnetic material in the path of said secondary flux means linking said secondary winding means,

said limiting cross section, upon its saturation, altering by its adjustment, the flux amplitude of the flux-magneto motive operating curve of said secondary flux means without essential change in the shape of said curve.

2. A transformer in accordance with claim 1, wherein said primary flux means comprises a high reluctance shunt arranged to bypass said secondary flux means.

3. A transformer in accordance with claim 1, wherein said secondary flux means comprises a ferromagnetic core structure, and

said adjustment means comprises a movable segment of said .core structure displaceable out of alignment therewith to reduce the effective cross section thereof over a signifi cant length thereof.

4. A transformer in accordance with claim 2, wherein said secondary flux means comprises a ferromagnetic core structure, and

said adjustment means comprises a movable segment of said core structure displaceable out of alignment therewith to reduce the effective cross section thereof over a significant length thereof.

5. A transformer in accordance with claim 3, wherein said core structure comprises a leg portion carrying said secondary winding means, I

and said moveable segment has parallel sides embraced between parallel sides of a slot in said core structure,

one of said sides of said slot being formed in said leg portion and being canted with respect to the flux axis in said leg portion.

6. A transformer in accordance with claim 4, wherein said core structure comprises a leg portion carrying said secondary winding means,

and said moveable segment has parallel sides embraced between parallel sides of a slot in said core structure,

one of said sides of said slot being formed in said leg portion and being canted with respect to the flux axis in said leg portion.

7. A transformer in accordance with claim 5, wherein said core structure comprises said leg portion and an end portion,

. and wherein said slot and said segment extend through said end portion, said sides of said segment being disposed to conduct flux between said leg portion and said end portion.

8. A transformer in accordance with claim 6, wherein said core structure comprises said leg portion and an end portion,

and wherein said slot and said segment extend through said end portion, said sides of said segment being disposed to conduct flux between said leg portion and said end portion.

9. A transformer in accordance with claim 7 wherein the end of said segment projecting into said leg portion is formed with an end face parallel to the flux axis of said leg portion.

'10. A transformer in accordance with claim 8 wherein the end of said segment projecting into said leg portion is formed with an end face parallel to the flux axis of said leg portion.

11. A transformer in accordance with claim 5 wherein said moveable segment is shaped and located to vary said limiting cross section along a significant length of said secondary flux means within said secondary winding means.

12. A transformer in accordance with claim 6 wherein said moveable segment is shaped and located to vary said limiting cross section along a significant length of said 5 secondary flux means within said secondary winding means. 

1. In a ferroresonant transformer, a magnetic core structure comprising primary flux means and secondary flux means, primary winding means linking said primary flux means and secondary winding means including resonating winding means linking said secondary flux means, the improvement comprising mechanical adjustment means operable upon said magnetic core structure in said secondary flux means to vary substantially and continuously the limiting cross section of magnetic material in the path of said secondary flux means linking said secondary winding means, said limiting cross section, upon its saturation, altering by its adjustment, the flux amplitude of the flux-magneto motive operating curve of said secondary flux means without essential change in the shape of said curve.
 2. A transformer in accordance with claim 1, wherein said primary flux means comprises a high reluctance shunt arranged to bypass said secondary flux means.
 3. A transformer in accordance with claim 1, wherein said secondary flux means comprises a ferromagnetic core structure, and said adjustment means comprises a movable segment of said core structure displaceable out of alignment therewith to reduce the effective cross section thereof over a significant length thereof.
 4. A transformer in accordance with claim 2, wherein said secondary flux means comprises a ferromagnetic core structure, and said adjustment means comprises a movable segment of said core structure displaceable out of alignment therewith to reduce the effective cross section thereof over a significant length thereof.
 5. A transformer in accordance with claim 3, wherein said core structure comprises a leg portion carrying said secondary winding means, and said moveable segment has parallel sides embraced between parallel sides of a slot in said core structure, one of said sides of said slot being formed in said leg portion and being canted with respect to the flux axis in said leg portion.
 6. A transformer in accordance with claim 4, wherein said core structure comprises a leg portion carrying said secondary winding means, and said moveable segment has parallel sides embraced between parallel sides of a slot in said core structure, one of said sides of said slot being formed in said leg portion and being canted with respect to the flux axis in said leg portion.
 7. A transformer in accordance with claim 5, wherEin said core structure comprises said leg portion and an end portion, and wherein said slot and said segment extend through said end portion, said sides of said segment being disposed to conduct flux between said leg portion and said end portion.
 8. A transformer in accordance with claim 6, wherein said core structure comprises said leg portion and an end portion, and wherein said slot and said segment extend through said end portion, said sides of said segment being disposed to conduct flux between said leg portion and said end portion.
 9. A transformer in accordance with claim 7 wherein the end of said segment projecting into said leg portion is formed with an end face parallel to the flux axis of said leg portion.
 10. A transformer in accordance with claim 8 wherein the end of said segment projecting into said leg portion is formed with an end face parallel to the flux axis of said leg portion.
 11. A transformer in accordance with claim 5 wherein said moveable segment is shaped and located to vary said limiting cross section along a significant length of said secondary flux means within said secondary winding means.
 12. A transformer in accordance with claim 6 wherein said moveable segment is shaped and located to vary said limiting cross section along a significant length of said secondary flux means within said secondary winding means. 